In normal brain function, one side of the brain (a hemisphere) controls the opposite side of the body. Thus, the right brain (right cerebral hemisphere) controls the left side of the body and the left brain (left cerebral hemisphere) controls the right side of the body. As such, when an individual has a stroke on one side of the brain, the opposite side of the body is typically left paralyzed or weak.
This opposite side control of the body by the brain has dictated how conventional brain computer interfaces have been designed. Conventional methods and systems have used brain control devices that use signals from the brain that correlate with contralateral arm movements (i.e., decoding signals from the brain that control the arm and hand on the opposite side of the body) to control an external object such as a robotic arm. These methods have not used signals taken from a cerebral hemisphere (i.e., left) and used ipsilateral movements (i.e., left) as a signal for overt control.
Financial cost of lifetime care for U.S. subjects suffering from hemispheric stroke is typically prohibitive. Hemiparesis is one of the most common reasons for their disability, and it is often hand function that is impaired. Motor cortex ipsilateral control to the affected limb is thought to play a role in recovery, yet its role in controlling ipsilateral limb movement conventionally has not been well understood. Functional studies in both normal and stroke-recovered subjects have demonstrated regions of activation with ipsilateral hand movements that are distinct from those motor sites associated with contralateral hand movements. Conversely, some groups have found ipsilateral activation not to correlate, or worse, to be indicative of poorer outcome in hemiparetic patients or subjects. The conventional techniques used in these studies, however, possess limitations of either spatial or temporal resolution, prohibiting a more definitive understanding of cortical processing of ipsilateral hand movements.
Therefore, there is a need to remedy the problems noted above and others previously experienced for using signals taken from the same side of the brain (ipsilateral) which correspond to movements from the same side of the body and to achieve an overt device control.